<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var obj = {
      uname: 'zs',
      qwer: 123
    }

    var uname = 'qwer'

    console.log( obj['uname'] )   //zs
    console.log( obj.uname )   //zs

    console.log( obj[uname] )   //123
    // console.log( obj.uname )   // zs
  </script>
</body>
</html>